But my main concern is that dumb users usually make up most of the
desktop market out there - and preaching to them that Linux will make
there virus problem go away is setting them up for a fall.

Bottom line, you're ignoring all the technical differences that make
Windows a wide open target, in comparison to Linux or Unix. No amount
of dumb users will overcome that fact. Then, good practices will go
further to reduce that risk and also it is virtually impossible for a
virus to get started, without some very deliberate action on the part of
the user. Also, some distros make it plain to users that running as
root is a dumb thing. In Windows, many apps require admin rights, just
to function. So if you're running such an app, any malware you get,
will have access to the entire system. On the other hand, with Linux,
if you need root privileges, you are specifically asked for them or
denied. This means that it's extremely difficult for malware to do
significant damage.